Touch senor, touch panel and electrode structure

ABSTRACT

The touch sensor includes a base, first and second electrodes that are formed on a main surface of the transparent base so as to face each other, and an extraction electrode that is formed on the main surface of the transparent base and extends from the second electrode. The first electrode has a shape which surrounds a portion of the second electrode. At least the extraction electrode is formed in a mesh pattern including a plurality of grids which are formed by thin metal wires.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of co-pending U.S. application Ser.No. 15/166,968 filed on May 27, 2016, which is a Continuation ofPCT/JP2014/077300 filed on Oct. 14, 2014, and which claims priorityunder 35 U.S.C § 119(a) to Japanese Patent Application No. 2013-247282filed Nov. 29, 2013. Each of the above applications is hereby expresslyincorporated by reference, in its entirety, into the presentapplication.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a touch sensor, and more particularly,to a touch sensor suitable for a touch panel and a touch panel.

2. Description of the Related Art

In recent years, a conductive film which is used in a touch panel hasdrawn attention as a conductive film provided in a display device. Thistouch panel is mainly applied to a small device, such as a PDA (portableinformation terminal) or a mobile phone. Increasing the size of thetouch panel may be considered for application to, for example, personalcomputer displays.

As the conductive film for a touch panel, the following examples havebeen proposed: an example in which a first electrode portion and asecond electrode portion face each other, with a substrate interposedtherebetween (JP2012-238278A); an example in which lead wire portionsare provided in a mesh pattern between a plurality of touch electrodeportions which are arranged on a main surface of a substrate at apredetermined interval (JP2012-043652A and JP2010-191504A); and anexample in which a touch electrode portion and an opposite electrode areformed on the same plane of a substrate (JP2010-541109A).

SUMMARY OF THE INVENTION

However, regarding the future trend, since a touch electrode and anextraction electrode are made of indium tin oxide (ITO), they have highelectrical resistance. Therefore, a structure will be considered inwhich an extraction electrode is formed by metal wires. Since theextraction electrode is formed in a visible region, there is a problemthat the extraction electrode is conspicuous, which results in areduction in visibility.

In contrast, a structure will be considered in which a plurality ofgrids formed by thin wires made of metal (thin metal wires) are arrangedto form an electrode, thereby reducing surface electrical resistance, asin JP2012-238278A, JP2012-043652A, JP2010-191504A, and JP2010-541109A.

However, in the electrode formed by the thin metal wires, the proportionof a conductive portion is lower than that in a transparent electrodefilm. Therefore, the initial capacitance between the electrodes issignificantly less than that in a transparent electrode film and thereis a limitation in improving the accuracy of detection. In particular,in a case in which the first and second electrode portions which faceeach other, with the substrate interposed therebetween, are provided,there is a concern that the distance between the electrodes willincrease and the initial capacitance between the electrodes willdecrease. When the initial capacitance is too large, a change incapacitance due to the approach or touch of a finger of a human isrelatively small and the accuracy of detection is reduced.

The invention has been made in view of the above-mentioned problems andan object of the invention is to provide a conductive film and a touchpanel in which an extraction electrode that is formed in a visibleregion is inconspicuous to improve visibility, the initial capacitancebetween electrodes increases to improve the accuracy of detection, andthe electrodes are formed on only one main surface of a base to reducecosts.

[1] According to a first aspect of the invention, there is provided aconductive film comprising a base, first and second electrodes that areformed on a main surface of the base so as to face each other, and anextraction electrode that is formed on the main surface of the base andextends from the second electrode. The first electrode has a shape whichsurrounds a portion of the second electrode. At least the extractionelectrode is formed in a mesh pattern including a plurality of gridswhich are formed by thin metal wires.

According to the aspect, the extraction electrode which is formed in avisible region is less likely to be seen and it is possible to improvevisibility. In addition, the initial capacitance between the firstelectrode and the second electrode can be increased and it is possibleto improve the accuracy of detection. The first electrode, the secondelectrode, and the extraction electrode can be formed on only one mainsurface of the base. Therefore, it is possible to simplify amanufacturing process, to reduce the number of processes, and to reducecosts.

[2] In the first aspect of the invention, a direction in which the thinmetal wire forming the mesh pattern extends may be inclined with respectto a direction in which the extraction electrode extends. In this case,it is possible to suppress the occurrence of moire.

[3] In the first aspect of the invention, when a total length of a pathin which a thin metal wire forming a portion that faces the secondelectrode in the outer periphery of the first electrode and a thin metalwire forming a portion that faces the first electrode in the outerperiphery of the second electrode face each other in parallel is L (mm)and an area that is surrounded by the outer periphery of the secondelectrode is A (mm²), a value of L (mm)/A (mm²) is preferably equal toor greater than 1.0 (mm⁻¹). According to the aspect, it is easy todetect a change in capacitance due to the touch or approach of a fingeror a pen and it is possible to improve the accuracy of detection of atouch position.

[4] In the first aspect of the invention, a pitch of the mesh pattern ispreferably equal to or greater than 200 μm and equal to or less than 300μm. According to the aspect, in a case in which the conductive film isused in a touch panel, it is possible to maintain transparency at a highlevel. For example, when the conductive film is attached to a displaypanel of a display device, it is possible to view a displayed imagewithout discomfort. In addition, it is possible to improve the accuracyof detection of a touch position.

[5] In the first aspect of the invention, a plurality of the secondelectrodes may be provided. The plurality of second electrodes may bescattered in the form of islands.

[6] In this case, the plurality of second electrodes which are scatteredin the form of islands may be arranged in a first direction. The firstelectrode may include a strip portion which extends in a strip shape inthe first direction and a surrounding portion which protrudes from thestrip portion and surrounds a portion of the second electrode. Accordingto the aspect, it is possible to widen the range of a sensing portionfor detecting the approach or touch position of a finger (referred to asa touch position) and to improve the accuracy of detection of the touchposition.

[7] A plurality of the first electrodes may be provided. The pluralityof second electrodes which are scattered in the form of islands may bearranged in a matrix. The plurality of first electrodes may be arrangedin a second direction perpendicular to the first direction.

[8] In this case, in each extraction electrode which extends from eachof the plurality of second electrodes arranged in the first direction, aregion which is adjacent to the corresponding first electrode may extendin the first direction. According to the aspect, the first electrode andthe second electrode can be formed on one main surface of the base. Inaddition, since the extraction electrode is formed in a mesh patternincluding a plurality of grids which are formed by thin metal wires, theextraction electrode is inconspicuous even when it is formed in avisible region.

[9] The first electrode and the second electrode may be formed in a meshpattern including a plurality of grids which are formed by thin metalwires. A dummy pattern which is formed by thin metal wires and is notconnected to the first electrode and the second electrode may be formedat least between the first electrode and the second electrode. Theplurality of grids may be uniformly arranged across at least the firstelectrode and the second electrode in a top view. According to theaspect, it is possible to prevent some of the thin metal wires or someof the electrodes from being seen. Therefore, visibility is improved.

[10] A dummy pattern which is formed by thin metal wires and is notconnected to a plurality of the extraction electrodes may be formedbetween the plurality of extraction electrodes. The plurality of gridsmay be uniformly arranged across the first electrode, the secondelectrode, and the extraction electrode in a top view. In this case,since a plurality of grids are uniformly arranged across the firstelectrode, the second electrode, and the extraction electrode in a topview of the conductive film, it is possible to prevent some of theextraction electrode from being seen and to further improve visibility.

[11] In the first aspect of the invention, each of the second electrodesmay have a shape in which a plurality of branch portions extendradially. The first electrode may have a shape which surrounds at leastthe plurality of branch portions of the second electrode. In this case,since a portion in which the first electrode and the second electrodeface each other has a complicated shape, it is possible to improve theinitial capacitance between the first electrode and the secondelectrode.

[12] In this case, the branch portions which extend radially in thesecond electrode may be scattered in the form of islands.

[13] The plurality of branch portions may be arranged in the firstdirection.

[14] In the first aspect of the invention, the first electrode may beformed in a mesh pattern including a plurality of grids which are formedby thin metal wires.

[15] In [1] to [8] and [11] to [14], the second electrode may be formedin a mesh pattern including a plurality of grids which are formed bythin metal wires.

[16] According to a second aspect of the invention, there is provided atouch panel comprising a conductive film that is provided on a displaypanel of a display device. The conductive film comprises a base, firstand second electrodes that are formed on a main surface of the base soas to face each other, and an extraction electrode that is formed on themain surface of the base and extends from the second electrode. Thefirst electrode has a shape which surrounds a portion of the secondelectrode. At least the extraction electrode is formed in a mesh patternincluding a plurality of grids which are formed by thin metal wires.

[17] In the second aspect of the invention, the conductive film mayinclude a sensor region that corresponds to a display screen of thedisplay panel and a terminal wiring region that corresponds to an outerperipheral portion of the display panel. The extraction electrode, thefirst electrode, and second electrode may be formed in the sensorregion.

As described above, according to the conductive film and the touch panelof the invention, since the extraction electrode which is formed in avisible region is less likely to be seen, it is possible improvevisibility. In addition, since the initial capacitance between theelectrodes is high, it is possible to improve the accuracy of detection.The electrodes can be formed on only one main surface of the base.Therefore, it is possible to reduce costs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view illustrating the structure of atouch panel according to an embodiment.

FIG. 2 is a cross-sectional view illustrating a conductive filmaccording to this embodiment together with a sensor body.

FIG. 3 is a plan view illustrating a pattern of a conductive portion(particularly, a first electrode, a second electrode, an extractionelectrode, a first terminal wiring portion, and a second terminal wiringportion) of the conductive film according to this embodiment.

FIG. 4 is an enlarged plan view illustrating an example of the patternof the first electrode, the second electrode, and the extractionelectrode and a dummy pattern illustrated in FIG. 3.

FIG. 5A is a plan view illustrating the pattern of some of the firstelectrodes corresponding to one column, a plurality of second electrodeseach of which is partially surrounded by the first electrode, and theextraction electrodes which extend from the second electrodes in thepattern illustrated in FIG. 3 and FIG. 5B is an enlarged viewillustrating a main portion of the pattern illustrated in FIG. 5A.

FIG. 6A is a plan view illustrating a first modification example of thepattern illustrated in FIG. 5A and FIG. 6B is an enlarged viewillustrating a main portion of the pattern illustrated in FIG. 6A.

FIG. 7A is a plan view illustrating a second modification example of thepattern illustrated in FIG. 5A and FIG. 7B is an enlarged viewillustrating a main portion of the pattern illustrated in FIG. 7A.

FIG. 8A is a plan view illustrating a third modification example of thepattern illustrated in FIG. 5A and FIG. 8B is an enlarged viewillustrating a main portion of the pattern illustrated in FIG. 8A.

FIG. 9A is a plan view illustrating a fourth modification example of thepattern illustrated in FIG. 5A and FIG. 9B is an enlarged viewillustrating a main portion of the pattern illustrated in FIG. 9A.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of a conductive film and a touch panelaccording to the invention will be described with reference to FIGS. 1to 9B. In the specification, for the term “to” indicating a numericalrange, values which are arranged before and after the term “to” are usedas a lower limit and an upper limit.

As illustrated in FIG. 1, a touch panel 10 according to this embodimentincludes a sensor body 12 and a control circuit (for example, an ICcircuit) (not illustrated). The sensor body 12 includes a conductivefilm 14 according to this embodiment and a cover layer 16 which is madeof, for example, glass and is stacked on the conductive film 14. Theconductive film 14 and the cover layer 16 are provided on a displaypanel 20 in a display device 18 such as a liquid crystal display. Theconductive film 14 include a sensor region 22 which corresponds to adisplay screen 20 a of the display panel 20 and a terminal wiring region24 (so-called frame) which corresponds to an outer peripheral portion ofthe display panel 20, as viewed from the top.

As illustrated in FIG. 2, the conductive film 14 includes a conductiveportion 28 which is formed on the surface of a transparent base 26 and atransparent adhesive layer 30 which is formed so as to cover theconductive portion 28.

In the sensor region 22, a first electrode 32A and a second electrode32B of the conductive portion 28 are formed on the surface of thetransparent base 26 so as to face each other and an extraction electrode34 of the conductive portion 28 is formed on the surface of thetransparent base 26 so as to extend from the second electrode 32B. Thefirst electrode 32A has a shape which surrounds a portion of the secondelectrode 32B. At least the extraction electrode 34 has a mesh pattern38 including a plurality of grids 36 which are formed by thin metalwires.

Specifically, a plurality of second electrodes 32B are provided. Theplurality of second electrodes 32B are scattered in the form of islands.More specifically, the plurality of second electrodes 32B which arescattered in the form of islands are arranged in a matrix in a firstdirection (y direction) and a second direction (x direction: a directionperpendicular to the first direction). It is preferable that a pluralityof first electrodes 32A are arranged in the second direction.

In this case, a portion in which the first electrode 32A and the secondelectrode 32B face each other is a sensing portion for detecting theapproach or touch position (referred to as a touch position) of afinger.

In particular, in this embodiment, for example, as illustrated in FIG.3, each first electrode 32A includes a strip portion 40 which extends ina strip shape in the first direction and a surrounding portion 42 whichprotrudes from the strip portion 40 and surrounds a portion of thesecond electrode 32B. For example, each second electrode 32B is formedin a rectangular shape in a top view. For example, three sides of eachsecond electrode 32B are surrounded by the surrounding portion 42 of thefirst electrode 32A. Therefore, the range of the sensing portion iswidened and it is possible to improve the accuracy of detection of thetouch position.

Each of the extraction electrodes 34 which are drawn from the pluralityof second electrodes 32B arranged in the first direction extends in thefirst direction in a region 44 (a region between the first electrodes32A) that is adjacent to the corresponding first electrode 32A.

A dummy pattern 46 which is not connected to the first electrode 32A andthe second electrode 32B may be formed at least between the firstelectrode 32A and the second electrode 32B. It is preferable that thedummy pattern 46 is formed in a mesh pattern 38 including a plurality ofgrids 36 which are formed by thin metal wires, similarly to the firstelectrode 32A and the second electrode 32B.

Therefore, the conductive film 14 has a shape in which a plurality ofgrids 36 are uniformly arranged across at least the first electrode 32Aand the second electrode 32B in a top view. It is possible to preventsome of the thin metal wires or some of the electrodes from being seenand visibility is improved.

Of course, the dummy pattern 46 which is formed by thin metal wires andis not connected to the extraction electrode 34 may be formed between aplurality of extraction electrodes 34. In this case, the conductive film14 has a shape in which a plurality of grids 36 are uniformly arrangedacross the first electrode 32A, the second electrode 32B, and theextraction electrode 34 in a top view. It is possible to prevent some ofthe extraction electrodes 34 from being seen and thus to further improvevisibility.

In the example illustrated in FIGS. 3 and 4, the dummy pattern 46 whichincludes a plurality of grids 36 formed by thin metal wires is formed ina region represented by a two-dot chain line in FIG. 3 (a region betweenthe first electrode 32A and the second electrode 32B, a region betweenthe first electrodes 32A adjacent to each other, a region between thefirst electrode 32A and the extraction electrode 34, a region betweenthe second electrode 32B and the extraction electrode 34, and a regionbetween the extraction electrodes 34), as illustrated in FIG. 4. FIG. 5Aillustrates the pattern of some of the first electrodes 32Acorresponding to one column, a plurality of second electrodes 32B, eachof which is partially surrounded by the first electrode 32A, and theextraction electrodes 34 which extend from the second electrodes 32B.

In the above-mentioned example, as schematically illustrated in FIG. 3and FIG. 5A, for example, three sides of each second electrode 32B aresurrounded by the surrounding portion 42 of the first electrode 32A.However, the second electrode 32B may be formed as follows.

That is, as illustrated in FIGS. 6A to 9B, each second electrode 32B mayhave a shape in which a plurality of branch portions 50 extend radiallyand the first electrode 32A may have a shape which surrounds at leastthe plurality of branch portions 50 of the second electrode 32B. In thiscase, a portion in which the first electrode 32A and the secondelectrode 32B face each other has a complicated shape. Therefore, it ispossible to increase the initial capacitance between the first electrode32A and the second electrode 32B and it is easy to detect a change incapacitance due to the touch or approach of a finger or a pen.

In general, in an electrode formed by thin metal wires, the percentageof a conductive portion is less than that in a transparent electrodefilm, such as an indium tin oxide (ITO) film. Therefore, the initialcapacitance between the electrodes is significantly less than that inthe transparent electrode film and there are limitations in improvingthe accuracy of detection. However, in this example, it is possible toincrease the initial capacitance between the first electrode 32A and thesecond electrode 32B. Therefore, it is possible to improve the accuracyof detection.

In particular, it is preferable that the electrode has the followingstructure. First, FIG. 5B, FIG. 6B, FIG. 7B, FIG. 8B, and FIG. 9B areenlarged views illustrating main portions illustrated in FIG. 5A, FIG.6A, FIG. 7A, FIG. 8A, and FIG. 9A, respectively. Here, attention is paidto a thin metal wire (referred to as a first thin metal wire 54A)forming a portion which faces one second electrode 32B in the outerperiphery (referred to first outer periphery 52A) of the first electrode32A. In addition, attention is paid to a thin metal wire (referred to asa second thin metal wire 54B) forming a portion which faces the firstelectrode 32A in the outer periphery (referred to as second outerperiphery 52B) of one second electrode 32B.

When the total length of a path in which the first thin metal wire 54Aand the second thin metal wire 54B face each other in parallel is L (mm)and an area surrounded by the second outer periphery 52B of the secondelectrode 32B is A (mm²), the value of L (mm)/A (mm²) is preferablyequal to or greater than 1.0 (mm⁻¹). When the value of L (mm)/A (mm²) isless than 1.0 (mm⁻¹), the initial capacitance between the firstelectrode 32A and the second electrode 32B is low and sensitivity isreduced.

Therefore, when the value of L (mm)/A (mm²) is 1.0 (mm⁻¹), it is easy todetect a change in capacitance due to the touch or approach of a fingeror a pen and it is possible to improve the accuracy of detection of atouch position. In FIGS. 5A to 9B, the dummy pattern 46 is notillustrated.

The total length L of the path may be calculated from the first thinmetal wire 54A or the second thin metal wire 54B. In the examplesillustrated in FIG. 5B, FIG. 6B, FIG. 7B, FIG. 8B, and FIG. 9B, thetotal length L of the path is calculated from the first thin metal wire54A. The sum of the lengths of the thin metal wires surrounded by aframe 56 represented by a two-dot chain line is the total length L ofthe path.

As such, in the conductive film 14 according to this embodiment, theextraction electrode 34 formed in the sensor region 22 is less likely tobe conspicuous and it is possible to improve visibility. In addition,the initial capacitance between the first electrode 32A and the secondelectrode 32B increases, which makes it possible to improve the accuracyof detection. The first electrode 32A, the second electrode 32B, and theextraction electrode 34 can be formed on only one main surface of thetransparent base 26. This structure makes it possible to simplify amanufacturing process and to reduce the number of processes. As aresult, it is possible to reduce costs.

In this embodiment, each of the first electrode 32A, the secondelectrode 32B, and the extraction electrode 34 is formed in the meshpattern 38. The direction in which the thin metal wire forming the meshpattern 38 extends is inclined with respect to the direction in whichthe extraction electrode 34 extends. The term “inclination” indicatesthat an angle formed between the extension direction of the thin metalwire and the extension direction of the extraction electrode 34 is anacute angle or an obtuse angle. When the angle is 0° or 90°, the thinmetal wire extends at a right angle with respect to the size of adisplay region of the display panel 20. As a result, moire is likely tooccur. In contrast, in this embodiment, as described above, since theextension direction of the thin metal wire is inclined with reference tothe extension direction of the extraction electrode 34, moire is lesslikely to occur.

A first terminal wiring portion 58A which is formed by metal wires andis electrically connected to the end of each first electrode 32A of theconductive portion 28 and a second terminal wiring portion 58B which isformed by metal wires and is electrically connected to the end of eachextraction electrode 34 of the conductive portion 28 are formed in theterminal wiring region 24.

In a case in which the conductive film 14 is used as the touch panel 10,the cover layer 16 is stacked on the conductive film 14 and a pluralityof first terminal wiring portions 58A and a plurality of second terminalwiring portions 58B which are drawn from the conductive film 14 areconnected to a control circuit (not illustrated) that controls, forexample, a scanning operation.

A self-capacitance method or a mutual capacitance method can bepreferably used as a touch position detection method.

In the self-capacitance method, the control circuit sequentiallysupplies a first pulse signal for detecting a touch position to thefirst terminal wiring portions 58A and sequentially supplies a secondpulse signal for detecting a touch position to the second terminalwiring portions 58B.

When a fingertip comes into contact with or approaches the upper surfaceof the cover layer 16, the capacitance between the ground (GND) and asensing portion which faces the touch position increases. Then, thewaveform of a transmission signal from the first electrode 32A and thesecond electrode 32B corresponding to the sensing portion is differentfrom the waveforms of transmission signals from the first electrodes 32Aand the second electrodes 32B corresponding to other sensing portions.Therefore, the control circuit calculates the touch position on thebasis of the transmission signal from the first electrode 32A and thesecond electrode 32B corresponding to the sensing portion.

In contrast, in the mutual capacitance method, the control circuitsequentially applies a voltage signal for detecting a touch position tothe second electrodes 32B and sequentially performs a sensing process(the detection of the transmission signal) for the first electrodes 32A.When a fingertip comes into contact with or approaches the upper surfaceof the cover layer 16, the floating capacitance of the finger is addedin parallel to parasitic capacitance (initial capacitance) in thesensing portion which faces the touch position. Then, the waveform ofthe transmission signal from the first electrode 32A corresponding tothe sensing portion is different from the waveforms of transmissionsignals from the first electrodes 32A corresponding to other sensingportions. Therefore, the control circuit calculates the touch positionon the basis of the order in which the voltage signal is supplied to thesecond electrodes 32B and the transmission signal supplied from thefirst electrode 32A.

The use of the touch position detection method, such as theself-capacitance method or the mutual capacitance method, makes itpossible to detect each touch position even when two fingers come intocontact with or approach the upper surface of the cover layer 16 at thesame time.

In addition, techniques related to a projected-capacitive detectioncircuit are disclosed in, for example, U.S. Pat. No. 4,582,955A, U.S.Pat. No. 4,686,332A, U.S. Pat. No. 4,733,222A, U.S. Pat. No. 5,374,787A,U.S. Pat. No. 5,543,588A, U.S. Pat. No. 7,030,860B, and US2004/0155871A.

Next, a preferred aspect of the conductive film according to thisembodiment will be described below.

(Transparent Base)

Examples of the transparent base 26 include a plastic film, a plasticplate, and a glass plate.

Examples of the raw material forming the plastic film and the plasticplate include polyesters, such as polyethylene terephthalate (PET) andpolyethylene naphthalate (PEN), polyolefins, such as polyethylene (PE),polypropylene (PP), polystyrene, and ethylene vinyl acetate (EVA),vinyl-based resins, polycarbonate (PC), polyamide, polyimide, acrylicresin, triacetylcellulose (TAC), and cycloolefin polymer (COP).

It is preferable that the transparent base 26 is a plastic film or aplastic plate made of a material having a melting point of about 290° C.or less, such as PET (melting point: 258° C.), PEN (melting point: 269°C.), PE (melting point: 135° C.), PP (melting point: 163° C.),polystyrene (melting point: 230° C.), polyvinyl chloride (melting point:180° C.), polyvinylidene chloride (melting point: 212° C.), or TAC(melting point: 290° C.). In particular, the transparent base 26 ispreferably a PET plate in terms of, for example, light transmittance andworkability. Since the conductive film 14 applied to the touch panelneeds to be transparent, it is preferable that the degree oftransparency of the transparent base 26 is high.

(Grid)

Each grid 36 has a polygonal shape. Examples of the polygon include atriangle, a quadrangle (for example, a square, a rectangle, aparallelism, or a trapezoid), a pentagon, and a hexagon. In addition,some of the sides forming the polygon may be curved.

It is preferable that the pitch of the mesh pattern 38 is in the rangeof 200 μm to 300 μm. Here, the pitch of the mesh pattern 38 means adistance between the center points (the centers of gravity) of twoadjacent grids 36. When the pitch is too small, the opening ratio andlight transmittance are reduced, which results in a reduction intransparency. On the other hand, when the pitch is too large, theopening ratio and light transmittance are improved, but the electricresistance of the first electrode 32A and the second electrode 32Bincreases. As a result, the accuracy of detection of the touch positionis reduced. In addition, when the pitch is too large, the distancebetween the first electrode 32A and the second electrode 32B which areadjacent to each other is large and the initial capacitance between thefirst electrode 32A and the second electrode 32B is low, which resultsin a reduction in the accuracy of detection. Therefore, in a case inwhich the pitch of the mesh pattern 38 is in the above-mentioned range,it is possible to maintain transparency at a high level. When theconductive film is attached to the display panel 20 of the displaydevice 18, it is possible to view a displayed image without discomfort.In addition, it is possible to improve the accuracy of detection of atouch position.

(Thin Metal Wire and Metal Wire)

The width of the thin metal wire is preferably equal to or greater than0.1 μm and equal to or less than 15 μm, more preferably equal to orgreater than 1 μm and equal to or less than 9 μm, and most preferablyequal to or greater than 2 μm and equal to or less than 7 μm. Thesurface electrical resistance of the first electrode 32A and the secondelectrode 32B is preferably in the range of 0.1 ohms/square to 100ohms/square. The lower limit of the surface electrical resistance ispreferably equal to or greater than 1 ohms/square, 3 ohms/square, 5ohms/square, and 10 ohms/square. The upper limit of the surfaceelectrical resistance is preferably equal to or less than 70 ohms/squareand 50 ohms/square.

The thin metal wires forming the first terminal wiring portion 58A andthe second terminal wiring portion 58B formed in the terminal wiringregion 24 and the thin metal wires forming the first electrode 32A, thesecond electrode 32B, and the extraction electrode 34 are made of asingle conductive material. The single conductive material is a metalmaterial, such as silver, copper, or aluminum, or an alloy including atleast one of them.

The opening ratio of the conductive film 14 according to this embodimentis preferably equal to or greater than 85%, more preferably equal to orgreater than 90%, and most preferably equal to or greater than 95% interms of visible light transmittance. The opening ratio is theproportion of a translucent portion other than the thin metal wires tothe conductive film. For example, the opening ratio of a square latticewith a wire width of 6 μm and a thin wire pitch of 240 μm is 95%.

As illustrated in FIG. 1, it is preferable that alignment marks 60 forpositioning which are used when the conductive film 14 is provided inthe display panel 20 are formed at, for example, the corners of theconductive film 14.

In the above-mentioned example, the conductive film 14 is applied to theprojected capacitive touch panel 10. However, the conductive film 14 maybe applied to a surface capacitive touch panel or a resistive touchpanel.

The conductive film 14 according to this embodiment may be used as anelectromagnetic wave shield film of the display device 18 or an opticalfilm provided in the display panel 20 of the display device 18, inaddition to the conductive film for the touch panel of the displaydevice 18. Examples of the display device 18 include a liquid crystaldisplay, a plasma display, an organic EL display, and an inorganic ELdisplay.

Next, a preferred method for forming, for example, the first electrode32A, the second electrode 32B, and the extraction electrode 34 areformed on the transparent base 26 will be described in brief.

For example, the first electrode 32A, the second electrode 32B, and theextraction electrode 34 can be preferably formed by a microcontactprinting patterning method or a silver salt method in order to obtain apattern with a small line width. It is preferable to use the silver saltmethod without using a stamp that wears out, in order to obtain a largenumber of repetitive random patterns.

The microcontact printing patterning method is a method which obtains apattern with a small line width using a microcontact printing method.The microcontact printing method is a method which brings a thiolsolution as ink into contact with a gold base, using an elastic stampmade of polydimethylsiloxane, to form a pattern of a monomolecular film(see Whitesedes et al., Angew. Chem. Int. Ed., 1998, vol. 37, p. 550).

For example, a representative process of the microcontact printingpatterning method is as follows. That is, first, a base is coated with ametal material (for example, a PET base is sputter-coated with silver).

Then, a mask of a monomolecular film is stamped onto the metal-coatedbase by the microcontact printing method. Then, the metal materialcoated on the base is removed by etching, except for the pattern belowthe mask.

For example, the detailed process of the method is described inparagraph <0104> of JP2012-519329A.

In contrast, the silver salt method is a method which exposes anddevelops a photosensitive material having a photosensitive layercontaining a silver salt to obtain a mesh pattern of the first electrode32A, a mesh pattern of the second electrode 32B, and a mesh pattern ofthe extraction electrode 34. The detailed process of the method isdescribed in paragraphs <0163> to <0241> of JP2009-004348A.

The invention can be used in combination with the techniques disclosedin Japanese Unexamined Patent Application Publications and InternationalPublication Pamphlets respectively listed in the following Tables 1 and2. For example, in Tables 1 and 2, notations of “JP”, “A”, and “WO”, areomitted.

TABLE 1 2004-221564 2004-221565 2007-200922 2006-352073 2006-2284692007-235115 2007-207987 2006-012935 2006-010795 2007-072171 2006-3324592009-21153 2007-226215 2006-261315 2006-324203 2007-102200 2006-2284732006-269795 2006-336090 2006-336099 2006-228478 2006-228836 2007-0093262007-201378 2007-335729 2006-348351 2007-270321 2007-270322 2007-1789152007-334325 2007-134439 2007-149760 2007-208133 2007-207883 2007-0131302007-310091 2007-116137 2007-088219 2008-227351 2008-244067 2005-3025082008-218784 2008-227350 2008-277676 2008-282840 2008-267814 2008-2704052008-277675 2008-300720 2008-300721 2008-283029 2008-288305 2008-2884192009-21334 2009-26933 2009-4213 2009-10001 2009-16526 2008-1715682008-198388 2008-147507 2008-159770 2008-159771 2008-235224 2008-2354672008-218096 2008-218264 2008-224916 2008-252046 2008-277428 2008-2419872008-251274 2008-251275 2007-129205

TABLE 2 2006/001461 2006/088059 2006/098333 2006/098336 2006/0983382006/098335 2006/098334 2007/001008

The invention is not particularly limited to the above-describedembodiment and various modifications and changes of the invention can bemade without departing from the scope and spirit of the invention.

For example, the first electrode 32A and the second electrode 32B may betransparent electrode films made of an indium tin oxide (ITO).

Example 1

Hereinafter, the invention will be described in more detail using thefollowing examples. In the following examples, materials, the amounts ofmaterials used, ratios, the content of processes, and the procedures ofprocesses can be appropriately modified without departing from the scopeand spirit of the invention. Therefore, the scope of the invention isnot limited by the following examples.

In Examples 1 to 5, errors in the detection of a touch position werechecked. Table 3 illustrates the breakdown and evaluation results ofExamples 1 to 5.

Example 1

(Photosensitive Silver Halide Material)

An emulsion was prepared which contained silver iodobromochlorideparticles having a sphere-equivalent average diameter of 0.1 μm (I=0.2%by mol, Br=40% by mol) dispersed in an aqueous medium containing 10.0 gof gelatin per 150 g of Ag.

In addition, K₃Rh₂Br₉ and K₂IrCl₆ were added to the emulsion at aconcentration of 10⁻⁷ (mol/mol-Ag) to dope the silver bromide particleswith Rh ions and Ir ions. Na₂PdCl₄ was added to the emulsion and theresultant emulsion was subjected to gold-sulfur sensitization, usingchlorauric acid and sodium thiosulfate. Then, the emulsion was used asan emulsion A. Then, the amount of K₃Rh₂Br₉ in the emulsion A wasreduced to prepare an emulsion of which the sensitivity was doubled. Theemulsion was used as an emulsion B.

(Formation of Photosensitive Layer)

Then, the emulsion and a gelatin hardening agent were applied onto thesurface of the transparent base 26 (which was made of PET in thisexample) with an A4 size (210 mm×297 mm) such that the amount of silverapplied was 10 g/m². At that time, the volume ratio of Ag/gelatin was2/1. The thickness of the transparent base 26 was 100 μm. Multi-layercoating was performed such that the amount of emulsion B in a lowerlayer was 5 g/m² and the amount of emulsion A in an upper layer was 5g/m². In this way, a photosensitive silver halide material having aphotosensitive layer with a thickness of 1.5 μm was obtained.

(Exposure)

An exposure process was performed for the obtained photosensitive silverhalide material. The photosensitive silver halide material was exposedin the pattern illustrated in FIGS. 3, 5A, and 5B. The exposure processwas performed through a photomask having the above-mentioned patterns,using parallel light emitted from a high-pressure mercury lamp as alight source.

(Development Process)

-   -   Formulation of 1 L of Developer

Hydroquinone 20 g Sodium sulfite 50 g Potassium carbonate 40 gEthylenediaminetetraacetie acid  2 g Potassium bromide  3 g Polyethyleneglycol 2000  1 g Potassium hydroxide  4 g pH adjusted to 10.3

-   -   Formulation of 1 L of Fixer

Ammonium thiosulfate solution (75%) 300 ml Ammonium sulfite monohydrate 25 g 1,3-Diaminopropanetetraacetic acid   8 g Acetic acid   5 g Aqueousammonia (27%)   1 g pH adjusted to   6.2

The exposed photosensitive material was developed under processingconditions (development: at 35° C. for 30 seconds; fixing: at 34° C. for23 seconds; and water washing: under running water (5 L/min) for 20seconds), using the above-described developing agent and an automaticdeveloping machine FG-710PTS manufactured by Fujifilm Corporation, toobtain a conductive film according to Example 1.

(Ratio of Total Length L of Path and Area A of Electrode)

In the obtained conductive film, the total length L (mm) of the path inwhich the first thin metal wire 54A and the second thin metal wire 54Bfaced each other in parallel and the area A (mm²) surrounded by thesecond outer periphery 52B of the second electrode 32B were calculatedand the ratio of the total length L of the path to the area A (the totallength L of the path/the area A) was calculated. In Example 1, the totallength L of the path/the area A was 0.8 (mm⁻¹).

Example 2

A conductive film according to Example 2 was obtained by the same methodas that in Example 1 except that the first electrode 32A and the secondelectrode 32B were formed in the pattern illustrated in FIGS. 6A and 6B,instead of the pattern illustrated in FIG. 3. In Example 2, the totallength L of the path/the area A was 0.9 (mm⁻¹).

Example 3

A conductive film according to Example 3 was obtained by the same methodas that in Example 1 except that the first electrode 32A and the secondelectrode 32B were formed in the pattern illustrated in FIGS. 7A and 7B,instead of the pattern illustrated in FIG. 3. In Example 3, the totallength L of the path/the area A was 1.0 (mm⁻¹).

Example 4

A conductive film according to Example 4 was obtained by the same methodas that in Example 1 except that the first electrode 32A and the secondelectrode 32B were formed in the pattern illustrated in FIGS. 8A and 8B,instead of the pattern illustrated in FIG. 3. In Example 4, the totallength L of the path/the area A was 1.2 (mm⁻¹).

Example 5

A conductive film according to Example 5 was obtained by the same methodas that in Example 1 except that the first electrode 32A and the secondelectrode 32B were formed in the pattern illustrated in FIGS. 9A and 9B,instead of the pattern illustrated in FIG. 3. In Example 5, the totallength L of the path/the area A was 1.5 (mm⁻¹).

(Detection Error)

Touch panels according to Examples 1 to 5 were manufactured using theconductive films according to Examples 1 to 5. A probe robotsequentially came into contact with 10000 predetermined contact pointswith a diameter of 5 mm on the surface of each touch panel to detecteach touch position. Then, the detection results of 10000 points werecompared with set values corresponding thereto. A case in which a 9973rdvalue from the smallest absolute value of a difference vector betweenthe detected position and the set position was equal to or greater than2 mm was represented by “N”. A case in which the 9973rd value was equalto or greater than 1.5 mm and less than 2 mm was represented by “C”. Acase in which the 9973rd value was equal to or greater than 1.3 mm andless than 1.5 mm was represented by “B”. A case in which the 9973rdvalue was less than 1.3 mm was represented by “A”.

(Evaluation Results)

The evaluation results are shown in the following Table 3.

TABLE 3 L/A Detection error (mm⁻¹) (%) Example 1 0.8 B Example 2 0.9 BExample 3 1.0 A Example 4 1.2 A Example 5 1.5 A

As can be seen from Table 3, the detection error is small in all ofExamples 1 to 5, which is preferable. In particular, in Examples 3 to 5,the total length L of the path/the area A is equal to or greater than1.0. Therefore, the evaluation result of the detection error is “A”,which is more preferable.

EXPLANATION OF REFERENCES

-   -   10: touch panel    -   12: sensor body    -   14: conductive film    -   18: display device    -   20: display panel    -   22: sensor region    -   24: terminal wiring region    -   26: transparent base    -   28: conductive portion    -   30: transparent adhesive layer    -   32A: first electrode    -   32B: second electrode    -   34: extraction electrode    -   36: grid    -   38: mesh pattern    -   40: strip portion    -   42: surrounding portion    -   46: dummy pattern    -   50: branch portion    -   52A: first outer periphery    -   52B: second outer periphery    -   54A: first thin metal wire    -   54B: second thin metal wire    -   58A: first terminal wiring portion    -   58B: second terminal wiring portion

What is claimed is:
 1. A touch sensor comprising: a base; a firstelectrode and a second electrode that are formed on a main surface ofthe base so as to face each other; and an extraction electrode that isformed on the main surface of the base and is extended from the secondelectrode, wherein the first electrode has a shape which surrounds aportion of the second electrode, and at least the extraction electrodeis formed in a mesh pattern including a plurality of grids which areformed by thin metal wires.
 2. The touch sensor according to claim 1,wherein a direction in which the thin metal wire forming the meshpattern extends is inclined with respect to a direction in which theextraction electrode extends.
 3. The touch sensor according to claim 1,wherein, when a total length of a path in which a thin metal wireforming a portion that faces the second electrode in the outer peripheryof the first electrode and a thin metal wire forming a portion thatfaces the first electrode in the outer periphery of the second electrodeface each other in parallel is L mm and an area that is surrounded bythe outer periphery of the second electrode is A mm², a value of L/A isequal to or greater than 1.0 mm⁻¹.
 4. The touch sensor according toclaim 2, wherein, when a total length of a path in which a thin metalwire forming a portion that faces the second electrode in the outerperiphery of the first electrode and a thin metal wire forming a portionthat faces the first electrode in the outer periphery of the secondelectrode face each other in parallel is L mm and an area that issurrounded by the outer periphery of the second electrode is A mm², avalue of L/A is equal to or greater than 1.0 mm⁻¹.
 5. The touch sensoraccording to claim 1, wherein a pitch of the mesh pattern is equal to orgreater than 200 μm and equal to or less than 300 μm.
 6. The touchsensor according to claim 2, wherein a pitch of the mesh pattern isequal to or greater than 200 μm and equal to or less than 300 μm.
 7. Thetouch sensor according to claim 3, wherein a pitch of the mesh patternis equal to or greater than 200 μm and equal to or less than 300 μm. 8.The touch sensor according to claim 1, wherein a plurality of the secondelectrodes are provided, and the plurality of second electrodes arescattered in the form of islands.
 9. The touch sensor according to claim8, wherein the plurality of second electrodes which are scattered in theform of islands are arranged in a first direction, and the firstelectrode includes a strip portion which extends in a strip shape in thefirst direction and a surrounding portion which protrudes from the stripportion and surrounds a portion of the second electrode.
 10. The touchsensor according to claim 9, wherein a plurality of the first electrodesare provided, the plurality of second electrodes which are scattered inthe form of islands are arranged in a matrix, and the plurality of firstelectrodes are arranged in a second direction perpendicular to the firstdirection.
 11. The touch sensor according to claim 10, wherein, in eachextraction electrode which extends from each of the plurality of secondelectrodes arranged in the first direction, a region which is adjacentto the corresponding first electrode extends in the first direction. 12.The touch sensor according to claim 11, wherein the first electrode andthe second electrode are formed in a mesh pattern including a pluralityof grids which are formed by thin metal wires, a dummy pattern which isformed by thin metal wires and is not connected to the first electrodeand the second electrode is formed at least between the first electrodeand the second electrode, and the plurality of grids are uniformlyarranged across at least the first electrode and the second electrode ina top view.
 13. The touch sensor according to claim 12, wherein a dummypattern which is formed by thin metal wires and is not connected to aplurality of the extraction electrodes is formed between the pluralityof extraction electrodes, and the plurality of grids are uniformlyarranged across the first electrode, the second electrode, and theextraction electrode in a top view.
 14. The touch sensor according toclaim 1, wherein each of the second electrodes has a shape in which aplurality of branch portions extend radially, and the first electrodehas a shape which surrounds at least the plurality of branch portions ofthe second electrode.
 15. The touch sensor according to claim 14,wherein the branch portions which extend radially in the secondelectrode are scattered in the form of islands.
 16. The touch sensoraccording to claim 15, wherein the plurality of branch portions arearranged in the first direction.
 17. The touch sensor according to claim1, wherein the first electrode is formed in a mesh pattern including aplurality of grids which are formed by thin metal wires.
 18. The touchsensor according to claim 1, wherein the second electrode is formed in amesh pattern including a plurality of grids which are formed by thinmetal wires.
 19. A touch panel comprising: the touch sensor according toclaim 1 that is provided on the display panel of the display device,wherein the touch sensor includes: the base; the first electrode and thesecond electrode that are formed on the main surface of the base so asto face each other; and the extraction electrode that is formed on themain surface of the base and is extended from the second electrode, thefirst electrode has a shape which surrounds a portion of the secondelectrode, and at least the extraction electrode is formed in a meshpattern including a plurality of grids which are formed by thin metalwires.
 20. The touch panel according to claim 19, wherein the touchsensor includes a sensor region that corresponds to a display screen ofthe display panel and a terminal wiring region that corresponds to anouter peripheral portion of the display panel, and the extractionelectrode, the first electrode, and second electrode are formed in thesensor region.
 21. A touch panel comprising: a base; a first electrodeand a second electrode that are formed on a main surface of the base soas to face each other; and an extraction electrode that is formed on themain surface of the base and is extended from the second electrode,wherein the first electrode has a shape which surrounds a portion of thesecond electrode, and at least the extraction electrode is formed in amesh pattern including a plurality of grids which are formed by thinmetal wires.
 22. An electrode structure comprising: a first electrodeand a second electrode facing each other; and an extraction electrodethat is extended from the second electrode, wherein the first electrodehas a shape which surrounds a portion of the second electrode, and atleast the extraction electrode is formed in a mesh pattern including aplurality of grids which are formed by thin metal wires.